Ligands used in affinity chromatography typically confer a high selectivity for the target molecule, thereby resulting in high yield, high purity and fast and economical purification of target molecules. Staphylococcus aureus Protein A-based reagents and chromatography matrices have found a widespread use in the field of affinity chromatography for capture and purification of antibodies and Fc-containing proteins as well as in analytical-scale antibody detection methods due to its ability to bind IgG, without significantly affecting the affinity of the immunoglobulin for antigen.
Accordingly, various reagents and media comprising Protein A-ligands have been developed and are commercially available, for example, ProSep®-vA High Capacity, ProSep® vA Ultra and ProSep® UltraPlus (MILLIPORE) and Protein A Sepharose™, MabSelect™, MabSelect Xtra™, MabSelect SuRe™ (GE HEALTHCARE), MabSelect SuRe™ LX and Poros MabCapture A™ (LIFE TECHNOLOGIES).
In order to maintain selectivity of the chromatography ligands including ligand bound solid supports such as SpA bound chromatography matrices, matrices have to be cleaned and are typically cleaned under acidic or alkaline conditions, e.g., with sodium hydroxide (NaOH). For example, a standard process which is used for cleaning and restoring the matrix is a cleaning-in-place (CIP) alkaline protocol, which typically involves treatment of the ligand bound matrix with NaOH concentration ranging from 0.05M to 1M, resulting in pH range 12.7 to 14.0. Typically, exposure of an affinity chromatography matrix to repeated CIP cycles results in significant loss of binding capacity of the matrix for a target molecule over time, requiring the use of a greater amount throughout the process, of often very expensive ligands which are bound to matrices. This is both uneconomical and undesirable as it results in the purification process becoming more expensive as well as lengthy.